On the farm today, autumn is in full swing and the witch hazel is too. Actually saw first Witch hazel flowers in early September. I think it has a pretty long bloom period. Not very showy in the landscape. You have to be close to it to notice, especially with all the yellow leaves nearby.
I think it would be fair as a autumn flowering bonsai, but leaves are big, and bark is mostly smooth, but dark. Like wisteria, hide it except autumn and maybe winter.